The present invention relates generally to pollutant abatement and, in particular, to an apparatus and process for eliminating and burning out pollutants in the interior air of large volume in an isolated space such as buildings, public transportation systems, and military vehicles contaminated by chemical and biological warfare agents. The chemical and biological warfare contaminants are eliminated by their exposure to the flames of the microwave plasma torches.
Protection of people against chemical and biological warfare agents is very important and is very necessary in the present world environment. The threat of chemical and biological warfare agents increases in a domestic terrorist attack and in worldwide military conflict. Year 2001 anthrax problems throughout the USA after 9-11 terror attack, 1995 sarin nerve gas attack on a Tokyo subway station, and the threat of toxic agents in 1991 Gulf War are a few examples of the worldwide threat of chemical and biological warfare agents. There are several categories of chemical warfare agents. They are (1) Nerve Warfare Agents, (a) Tabun, GA: CH3)2Nxe2x80x94P(xe2x95x90O)(xe2x80x94CN)(xe2x80x94OC2H5, (b) Sarin, GB: CH3xe2x80x94P(xe2x95x90O)(xe2x80x94F) (xe2x80x94OCH(CH3)2, (c) Soman, GD: CH3xe2x80x94P(xe2x95x90O)(xe2x80x94F)(xe2x80x94CH(CH3)C(CH3)3, (d) Cyclohexyl methylphosphonofluoridate, GF: CH3xe2x80x94P(xe2x95x90O)(xe2x80x94F)(cykloxe2x80x94C6H11), (e) Methylphosphonothioic acid S-(2-(bis(1-methylethyl)amino)ethyl) O-ethyl ester, VX: CH3xe2x80x94P(xe2x95x90O)(xe2x80x94SCH2CH2N[CH(CH3)2]2) (xe2x80x94OC2H5), (f) GE: Phosphonofluoridic acid, ethyl-, isopropyl ester, (g) VE: Phosphonothioic acid, ethyl-, S-(2-(diethylamino)ethyl) O-ethyl ester, (h) VG: Amiton, and (i) VM: Phosphonothioic acid, methyl-, S-(2-(diethylamino)ethyl) O-ethyl ester, (2) Blister and Vesicant Warfare Agents, (a) Lewisite (L), (b) Mustard-Lewisite (HL), (c) Nitrogen Mustards (HN-1, HN-2, HN-3), (d) Phosgene Oxime (CX), and (e) Sulfur Mustards (H, HD, HT), (3) Blood Warfare Agents, (a) Cyanogen Chloride (CK), and (b) Hydrogen Cyanide (AC), and (4) Pulmonary Warfare Agents, (a) Chlorine, (b) Chloropicrin (PS), (c) Diphosgene (DP), (d) Phosgene (CG). There are also several biological warfare agents such as Anthrax, Botulinum Toxins, Brucellosis, Cholera, Clostridium Perfringens Toxins, Congo-Crimean Hemorrhagic Fever, Ebola Haemorrhagic Fever, Melioidosis, Plague, Q Fever, Ricin, Rift Valley Fever, Saxitoxin, Smallpox, Staphylococcal Enterotoxin B, Trichothecene Mycotoxin, Tularemia, Venezuelan Equine Encephalitis. There may be other chemical and biological warfare agents not listed above. But, those warfare agents must be also eliminated by the present invention.
The purpose of the present invention is a rapid and effective elimination of toxic substances in the interior air in an isolated space such as buildings, public transportation systems, and military vehicles. The buildings, where the interior air must be purified, can be the personal dwellings, apartment buildings, office buildings, school buildings, government buildings, and the commercial buildings. The public transportation system includes automobiles, cars, buses, trains, ships, commercial airline airplanes, and the subway railroad system. The military vehicles mentioned are military trucks, armored personnel carriers, military buses, tanks, military ships, airplane carries, helicopters, and military airplanes. The toxic warfare agents mentioned above have been traditionally incinerated by burn scrubbers. These burners tend to be large, inefficient, and expensive. On the other hand, the microwave plasma torch operated at the atmospheric pressure is compact enough to be installed in a narrow space and is effective to eliminate the toxic agents diluted in a large flow rate of air.
Pollution control with respect to contaminated air as a carrier gas was proposed in U.S. Pat. No. 5,468,356 issued to Uhm, one of the present inventors, on Nov. 21, 1995. In that invention, contaminated air is exposed to microwave-generated plasma for oxidation by atomic oxygen without bulk heating within a simple cylindrical waveguide cavity at the room temperature. Further, such plasma is generated within the cavity by introduction of high-power microwave radiation passing through a weak electric field to achieve air purification despite low electron energy. Pollution control with respect to contaminated air as a hot carrier gas was proposed in U.S. Pat. No. 5,830,328 issued to Uhm, one of the present inventors, on Nov. 3, 1998. The plasma generated in a hot gas like discharge gas from a combustion engine or like the discharge gas from an incinerator may oxidize the contaminants, purifying the discharge air. The present invention is a combination of the above two inventions, making use of an intense electric field in the microwave radiations and use of the hot air in the torch flames of the present invention.
It is therefore an important object of the present invention to enhance the electric field strength of the microwave radiation in order to achieve elimination of toxic warfare agents in a carrier gas by exposure to a plasma torch generated by concentration of the microwave on a small spot.
Other object of the present invention is to simultaneously provide an elimination and burnout system that is effective against a wide range of chemical and biological warfare agents with several plasma torches connected in series.
Another object is to overcome difficulties heretofore experienced in achieving efficient and rapid elimination of the toxic agents by oxidation with several plasma torches connected in series.
Additional objects, advantages and novel features of the invention will be explained in part in the following description, and will be apparent to those skilled in the following experiment.
The present invention is the apparatus for simultaneous elimination and burnout of chemical and biological warfare agents diluted in air with several microwave plasma torches connected in series. Particularly, the apparatus is useful for purifying the interior air of large volume in an isolated space such as buildings, commercial transportation systems, and military vehicles contaminated with chemical and biological warfare agents. High electric field strength and high-energy electrons provided by the plasma torch are needed to eliminate and bum out chemical and biological warfare agents. The microwave plasma torches are connected in series so that the contaminant air stream to be purified passes sequentially from one plasma torch to the next, thereby increasing the required residence time for optimum effect. The high temperature flames of microwave plasma torches create a unique environment for efficient chemical reactions. Prolonging this unique environmental condition by sequential connection of optimum number of microwave plasma torches is critically important for rapid purification of a large volume of contaminated air, creating a synergic effect caused by multiple plasma torches. The number of the plasma torches is empirically determined.
The present invention is made of the magnetrons used in home microwave ovens. These magnetrons are inexpensive, commercially available and compact. They are operated at a frequency of 2.45 GHz and their power is in the range of 0.6xcx9c1.4 kW. The microwave intensity with a frequency of 2.45 GHz from a magnetron is highest at the discharge tube. These intense microwaves at the discharge tube induce an intense electric field, initiating electrical breakdown in the carrier gas containing chemical and biological warfare agents. The plasma torch generated by the electrical breakdown due to the microwave electric field eliminates and burns out chemical and biological warfare agents by oxidation, by molecular breakdown, and by hot gases. The atmospheric plasma abatement system, which is simple and cost-effective, is the most suitable for purification of air contaminants. The elimination experiment of any chemical warfare agent is almost impossible in an ordinary laboratory due to safety issues. In this context, the experimentalists traditionally carry out a simulated experiment by making use of toluene gas. Elimination efficiency of toluene as one simulated agent was experimentally measured by a gas chromatography system. For same reason, the biological warfare agents are not used in an ordinary laboratory. Therefore, the vitrification and burnout of dried and pulverized sewage sludge powder as the biological simulated agent were carried out.